1. Technical Field
The present disclosure relates to a position detection device for detecting a relative position of one resonator to another resonator. The present disclosure also relates to a power transmission apparatus and a power reception apparatus including such a position detection device and implementing wireless power transfer for transmitting power in a non-contact manner, and also to a wireless power transfer system including such a power transmission apparatus and power reception apparatus.
2. Description of the Related Art
These days, for audiovisual (AV) machines and electronic devices involving the mobility, such as cellular phones and electric vehicles, various wireless power transfer systems for performing wireless charging are being developed. There are various methods for implementing wireless power transfer technologies, such as an electromagnetic induction method and a magnetic-field resonance method utilizing a plurality of coils opposing each other, and an electric-field coupling method utilizing a plurality of metal plates opposing each other. An example of a wireless power transfer system utilizing the electromagnetic induction method is disclosed in International Publication No. 2011/033660 pamphlet. This wireless power transfer system includes a power transmission apparatus having a power transmission coil (power transmission antenna) and a power reception apparatus having a power reception coil (power reception antenna). Then, a magnetic field generated by the power transmission coil is trapped by the power reception coil, thereby transmitting power from the power transmission apparatus to the power reception apparatus without involving direct contact of electrodes.
International Publication No. 2007/107642 pamphlet discloses an example of a wireless power transfer system utilizing the electric-field coupling method.
In the above-described wireless power transfer systems, if the power transmission coil and the power reception coil are displaced from each other when performing power transfer, not only the power transmission efficiency is decreased, but also a metallic foreign substance disposed outside the power transmission coil or the power reception coil may be heated due to leakage flux from the power transmission coil or the power reception coil. Accordingly, the positional adjustment of a power transmission coil and a power reception coil may be important for implementing safe, high-efficiency wireless power transfer.